Page 157 - Materials Chemistry, Second Edition

140 Practical Design Calculations for Groundwater and Soil Remediation

Four different configurations of slurry bioreactors in the PFR mode are
considered. Determine the final effluent concentration from each of these
arrangements and whether it meets the cleanup requirement:

(a) One 4-m reactor
3
(b) Two 2-m reactors in series
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(c) One 1-m reactor followed by one 3-m reactor
3
3
(d) One 3-m reactor followed by one 1-m reactor
3
3
Solution:
(a) For the 4-m reactor,
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the residence time = V/Q = 4 m /(0.04 m /min) = 100 min
3
3
Q, C in Q, C out
4 m 3

Use Equation (4.24) to find the final effluent concentration:

C out C out − (0.1)(100) − 10
= = e = e
C in 1,800

C = 0.082 mg/kg (It is below the cleanup level.)
out
3
(b) For the two 2-m reactors,
3
3
the residence time = V/Q = 2 m /(0.04 m /min) = 50 min each
Q, C 0 Q, C 1 Q, C 2
2 m 3 2 m 3

Use Equation (4.29) to find the final effluent concentration:

 C 2   C 2   C 1 
=   =     = e [ ]× e [ ]
C 2 − (0.1)(50) − (0.1)(50)
C 0  1,800  C 1   C 0 
= e − (0.1)(50 50) = e − 10
+
C = 0.082 mg/kg (It is below the cleanup level.)
out
(c) The residence time of the first reactor
= 1 m /(0.04 m /min) = 25 min
3
3